Hydraulic apparatus

ABSTRACT

A swashplate pump or motor having a rotary cylinder block, cylinders in the block parallel to or inclined to the rotation axis, a valve on which the block is arranged to rotate and an inclinable swashplate located adjacent to one end of the cylinder block and engageable by pistons in the cylinders either directly or through the medium of slippers whereby the pistons are reciprocated when the block rotates. The pump or motor includes a structural member formed in one piece having, A. A FLAT VALVE SURFACE AGAINST WHICH THE CYLINDER BLOCK ROTATES, B. A CYLINDRICAL BEARING SURFACE SURROUNDING PART OF THE CYLINDER BLOCK AND IN WHICH THE CYLINDER BLOCK ROTATES, C. APERTURES TO SUPPORT A TRANSVERSE SHAFT CARRYING THE SWASHPLATE FOR TILTING MOVEMENT, AND D. A SERVOMOTOR CYLINDER BORE TO HOUSE A SERVO PISTON ARRANGED TO ADJUST THE INCLINATION OF THE SWASHPLATE ABOUT THE AXIS OF THE TRANSVERSE SHAFT.

[ Mar. 7, 1972 [54] HYDRAULIC APPARATUS Kenneth Raymond Boydell, Bredons Hardwicke, near Tewkesbury, England Dowty Technical Developments Limited, Brockhampton, Cheltenham, England 22 Filed: Sept. l9, 1969 211 Appl.No.: 859,447

[ 72] Inventor:

[73] Assignee:

[30] Foreign Application Priority Data Sept. 20, 1968 Great Britain ..44,774/68 U.S. pistons are reciprocated when the rotates The pump or [51] Int. Cl ..F04D 1/26 motor includes a structural member formed in one piece hay- [58] Field of Search ..9l/47, 48, 505, 506, 475, 507; ing,

asaaa sy l es rf gyymwthesfieqssbl [56] References Cited rotates b. a cylindncal bearing surface surrounding part of the UNITED STATES PATENTS cylinder block and in which the cylinder block rotates,

c. apertures to support a transverse shaft carrying the 2,292,125 8/1942 lfield ..4i7/203 swashplate for tilting movement and 24O70l3 9/1946 [field 91/47 (1. a servomotor cylinder bore to house a servo piston 2'554'047 5/1951 Moon 91/505 arranged to adjust the inclination of the swashplate 2564263 8/195l [field 91/453 about the axis of the transverse shaft. 3,108,544 10/1963 Pesce ..91/505 M 3,266,434 8/1966 McAluay 417/222 3,496,833 2/1970 Kobelt ..9l/49 H 2 Claims, 4 Drawing Figures FOREIGN PATENTS OR APPLICATIONS 500,937 2/1939 Great Britain ..9l/475 926,234 4/1947 France ..9l/472 Primary Examiner-William L. Freeh Attorney-Young & Thompson 57] ABSTRACT A swashplate pump or motor having a rotary cylinder block, cylinders in the block parallel to or inclined to the rotation axis, a valve on which the block is arranged to rotate and an inclinable swashplate located adjacent to one end of the cylinder block and engageable by pistons in the cylinders either directly or through the medium of slippers whereby the FATENTEUMAR v 1912 I "3,647, 321

SHEET- 1 OF 3 A 68 FIG.

BYfmwy ram ATTORNEYS HYDRAULIC APPARATUS This invention is an improvement in or modification of the invention disclosed in the cognate complete specification filed in respect of our copending application Ser. No. 694,717. More particularly this invention relates to hydraulic pumps and motors of the kind including, a rotary cylinder block having cylinders parallel to or inclined to the rotation axis, a valve on which the block is arranged to rotate and an inclinable swashplate located adjacent to one end of the cylinder block and engageable by pistons in the cylinders either directly or through the medium of slippers whereby the pistons are reciprocated when the block rotates. This kind of pump or motor will hereinafter be referred to as a swashplate device.

In accordance with the present invention a swashplate device includes a structural member formed in one piece havmg,

a. a flat valve surface against which the cylinder block rotates,

b. a cylindrical bearing surface surrounding part of the cylinder block and in which the cylinder block rotates,

c. apertures to support a transverse shaft carrying the swashplate for tilting movement, and

d. a servomotor cylinder bore to house a servo piston arranged to adjust the inclination of the swashplate about the axis of the transverse shaft.

Any conventional wear or friction reducing means may be provided for either of the surfaces, the apertures or the cylinder bore.

The servo piston may be provided with only one area subjected to servo liquid at pressure and the transverse shaft may be offset from the rotation axis of the block such that the reaction of the pistons in the cylinders in the cylinder block produces a torque on the swashplate about the axis of the shaft which is opposed by the force generated by the servo piston.

Spring loading may act to hold the cylinder block on the valve and may also react on the swashplate to generate torque about the transverse shaft axis.

The liquid servo pressure fed to act on the servo piston may be the pressure generated at the junction of a pair of restrictors connected in series from the high-pressure port in the valve of the swash plate device to a low-pressure zone, one of the restrictors being variable to adjust the servo pressure.

The variable restrictor may either be within the servo piston or at a position fixed relatively to the structural member.

The servo cylinder may be arranged so that its axis is parallel with the cylinder block axis.

Where the variable restrictor is carried by the servo piston a manual control for the variable restrictor may comprise a rod extending through the servo cylinder for adjustment by a manual control member whereby the piston will move as a result of servo pressure and swashplate torque to assume a position dependent on the manually selected position of the control rod controlling the variable restrictor in the piston.

One embodiment of the invention for use as a pump will now be particularly described with reference to the accompanying drawings in which,

FIG. 1 is a cross section through the pump,

FIG. 2 is a composite cross section taken on the line lI-II of FIG. 1,

FIG. 3 is a perspective view of the pump, and

FIG. 4 is an end elevation showing the pump mounting.

In the drawings the structural member of the pump is an aluminum casting and it comprises three integrally formed parts indicated as the valve I, the casing 2 and the servo cylinder 3. The valve 1 has a flat valve surface 4 which contains a highpressure delivery port 5 of conventional kidney shape connected to a delivery passage 6 which terminates as a screwthreaded connection 7 on the outside of the valve 1. A plurali-. ty of mounting lugs 8 are provided around the periphery of the valve I for securing the pump in its operative position, the pump being correctly located by a cylindrical boss 9 adapted to fit in a corresponding hole on a driving motor or engine. 1

The hollow casing 2 is closed at the end remote from the valve 1 by means of a cover 11 of pressed sheet metal secured in a large circular recess 12 by means of a circlip 13. A rubber seal 14 ensures a liquidtight connection between the casing 2 and the cover 11.

In the casing 2 a cylinder block 15 of cast iron is arranged for rotation about the axis A--A. The cylinder block 15 includes a flat surface 16 bearing against the valve surface 4. Within the block there are five regularly spaced cylinders 17 all of whose axes are parallel to the rotation axis AA of the block. Each cylinder 17 includes a port 18 opening into the surface 16, the ports 18 being arranged to cooperate with the main pressure port 5 during the rotation of the cylinder block 15. At a position remote from the surface 16 the cylinder block includes an integrally fonned skirt 19 around which is formed a cylindrical bearing surface 21 which efiectively surrounds the cylinder block. Within the casing 2 adjacent to the cylindrical bearing surface 21 an internal cylindrical bearing surface 22 is formed which directly engages the cylindrical bearing surface 21 of the block to locate the block for rotation.

Five passages 24 are formed within the cylinder block one between each adjacent pair of cylinders. Each passage opens from the surface of the block remote from the valve surface 4 between paddles or vanes 25 formed on the cylinder block 15 within the casing 2. A recess 26 is formed in the valve surface 4, the inner portion of this recess cooperating with the cylinder ports 18 at a position (not shown) so as to form an inlet port while the outer portion of this recess opens into the spaces between the vanes 25.

The casing 2 remote from the valve includes a pair of integrally formed bosses 27 bored transversely to produce a pair of spaced apertures 28. Between the bosses 27 a swashplate 29 is mounted on a shaft 31 by means of a cylindrical bore 32 extending through the swashplate. The swashplate includes a flat swash surface 33 facing the cylinder block 15.

Within each cylinder 17 a piston 34 and a compression spring 35 are located, the spring acting to urge the piston outwardly from the cylinder. At its outer end each piston 34 is formed with a spherical socket 36 into which a ball 37 is secured. The ball 37 is integrally connected to a slipper 38 engaging the swash surface 33. A hydraulic passage 39 within each piston 34 gives access to the socket 36 for lubrication and also connects to a passage 41 in the ball which feeds liquid at pressure through a restrictor 42 to a recess 43 in the slipper surface in contact with the swash surface 33. The recess is conventionally arranged so that hydraulic pressure acting in the recess will almost completely balance the hydraulic load acting on the piston.

A retaining plate 44 includes five apertures 45 engaged one on each slipper 38. Centrally the retaining plate 44 reacts against a ball 46 carried by a pad 47 slidably mounted in a central bore 48 in the cylinder block, a compression spring 49 reacting between the block 15 and the pad 47 serving simultaneously to urge the block against the valve surface 4 and also to urge the retaining plate 44 to maintain the slippers in contact with the swash surface.

A splined aperture 51 is provided centrally within the cylinder block to open into a comparatively large aperture 52 extending through the valve 1. A drive shaft (not shown) may be inserted through the aperture 52 to engage the splined aperture 51 to drive the cylinder block. A seal 53 may engage between the valve and the cylinder block in the manner disclosed in our copending application Ser. No. 838,607. To prevent hydraulic leakage between the bore 48 and the aperture 52 the bore 48 is sealingly closed by means of a plug 54.

The servo cylinder 3 has a servo piston 55 slidably mounted therein one end being connected by means of a pivotal pin 56 to a link 57 which in turn is connected by a pivotal pin 58 to a lever 59 extending from the swashplate 29. In the drawing the swashplate is shown at a position of maximum inclination and the servo piston 55 is in a corresponding position.

The small diameter bore 61 within the piston 55 receives one end of a rod 62 which extends from the end of the servo cylinder 3 adjacent to the valve 1. The end of the cylinder 3 adjacent to the valve 1 has a plug 63 inserted thereinbeing retained in position by a cap 64 and circlip 65. A central bore 66 through the plug 63 locates the rod 62 for sliding movement, a suitable seal on the rod 62 preventing leakage of liquid. The end of the cylinder 3 adjacent to the valve 1 is formed in an extension 67 from the valve 1 but integral therewith. A rotary controlled spindle 68 is suitably mounted in bearings in the extension 67, the spindle 68 carrying a lever 69 which extends into a chamber 71 within the plug 63 to engage in a recess 72 in the end of the rod 62 such that rotation of the spindle 68 will cause endwise movement of the rod 62. A passage 73 extends in the valve 1 from the delivery passage 6 to intersect the cylinder bore 3. At the position of intersection the plug 63 includes a peripheral groove 74 from which a small hole is bored to form the restrictor 75 which connects through passage 76 in plug 63 to the working space 77 between the plug 63 and the piston 55.

The end of the rod 61 includes a counter bore 78 from which a pair of radially directed control ports 79 open into the working space 77. The rod 62 is located for limited motion within the piston bore 61 by means of a transverse pin 81 loosely engaging a transverse hole in the rod 62. The movement permitted for the rod 62 relative to the piston will vary the opening of the ports 79 over the edge of the bore 61 into the working space 77. The ports 79 and the cooperating edge of the bore 61 form a variable restrictor adjustable by movement of rod 62.

The end of the servo bore 3 opposite to the valve 1 is formed as a screw-threaded inlet connection 82 and liquid entering connection 82 may pass into the casing through a eutaway portion 83 through which the lever 59 extends to the link 57. The liquid entering the pump thereby flows firstly over the swashplate 29 before entering the passages 24.

in operation the cylinder block is rotatably driven by a drive shaft inserted through the large aperture 52 and rotation of the cylinder block causes reciprocation of the pistons in the cylinders by virtue of the fact that the slippers are held against the swashplate 29. During rotation the liquid fed from the inlet connection 82 flows around the swashplate and into the passages 24 being there induced by centrifugal pumping action to flow to the recess 26 and thence into the cylinder ports 18 during the period when the pistons are moving outwardly from their cylinders. Cylinder ports 18 connect through the main delivery port when the pistons are urged into their cylinders such liquid being delivered at high pressure through the delivery passage 6.

The fact that the swashplate is inclined causes considerable side thrust to be exerted on the cylinder block through the pistons and the axial extent of the bearing surfaces 21 and 22 is such that the line of action of side force exerted on the pistons by the swashplate will pass directly through the bearing surfaces without creating tilting movement of the cylinder block.

The offset relation of the shaft 31 having regard to the rotation axis A-A of the cylinder block results in a torque being generated on the swashplate 29 about the axis of the shaft 31 which will tend to reduce the inclination of the swashplate to zero, the limit of such movement being the engagement of a head 84 of rod 62 against the cap 64. Maximum inclination of the swashplate is limited by the engagement of the head 84 against the end of chamber 71 opposite to the cap 64. The required angular setting for the swash plate is selected by the spindle 68 which adjusts the axial position of the rod 62. Movement of the rod 62 will adjust the variable restrictor formed by ports 79 to control the pressure developed within the working space 77 by virtue of the series connection of the fixed restrictor 75 with the variable restrictor between the high-pressure connection 6 and the low pressure interiorly of the casing 2. The pressure within the working space 77 urges the swashplate towards its maximum inclination whilst the torque developed on the swashplate itself urges it to the minimum inclination. Simple adjustment of the spindle 68 will therefore control pressure in the working space 77 to cause the swashplate to take up an angular position which is in proportion to the angular setting of the spindle 68.

In the manufacture of the pump the passage 73 is formed by drilling a hole exteriorly of the pump casing through the servo cylinder 3 and into the delivery passage 6, this drilling 73 being inclined to the axis of the servo cylinder 3 so that when plug 63 is inserted the groove 74 connects only to the part of the passage 73 in connection with delivery passage 6. The outer end of the passage 73 may be closed by a simple plug 85 but leakage of high-pressure liquid from the outer end of passage 73 is prevented by the provision of a pair of seals 86 around the plug 63 on either side of the position at which cylinder 3 is intersected by the outer end of passage 73.

The grade of aluminum alloy selected for the structural member forming the casing, the valve, the bosses and the servo cylinder is chosen to have the necessary strength to cater for the intended operating pressures of the pump. While the described embodiment shows direct bearing engagement between the cylindrical surfaces 21 and 22 it will be appreciated that the surfaces 21 and 22 may be provided with an interposed shell of wear-resisting material or other conventional bearing means. The flat surface 4 of the valve engages directly with the flat surface 16 of the block and the design of g the ports in these surfaces is preferably such that a hydraulic force will act between them to urge the cylinder block away from the valve, the force being only slightly less than the hydraulic force urging the cylinder block on to the valve by virtue of liquid at pressure in the cylinders. It is within the scope of the present invention for a thin wear plate to be carried on the flat surface 4 in order to reduce wear. it is also within the scope of the invention for the apertures 28 and the servo cylinder 3 to be provided with suitable bearing sleeves or the like to reduce friction and wear.

While the described embodiment is a pump, a motor is also within the scope of the invention. For use as a motor the illustrated embodiment would necessarily be modified to ensure connection of the main ports in the valve surface 4 to highand low-pressure supplies to cause cylinder block rotation in the required direction.

in the manufacture of the describedembodiment the rotating cylinder block assembly and the swash plate may be assembled into position by entering them through the opening 12 and then entering the shaft 31 through the apertures 28 and the bore 32 to locate the swashplate in place. The servo piston 55, control rod 62 and plug 63 are entered into the servo cylinder bore 3 from the end adjacent the valve 1, the link 57 having been previously secured by the pin 56 to the servo piston. The final entry of the pin 58 into its operative position is effected by the provision of a removable plug 87 which enters the bore 3 adjacent to the inlet connection 82. With the plug 87 removed the pin 58 is inserted to connect link 57 to lever 59, the pin being locked in position by means such as a circlip 88 secured to the pin 58 through the open end 12 of the casing. The cover 11 and the cap 64 may then be secured in their respective positions by means of circlips l3 and 65 to complete assembly of the pump.

lclaim:

1. A swashplate device comprising a rotary cylinder block having cylinders parallel to or inclined to the rotation axis, a tiltable swashplate, a one-piece transverse through shaft carrying the swashplate for tilting movement, a servo piston arranged to adjust the inclination of the swashplate about the axis of the transverse shaft, and a structural member formed in one piece and having a flat valve surface in contact with which the cylinder block rotates, a cylindrical bearing surface surrounding part of the cylinder block and in contact with which the cylinder block rotates, apertures which support said shaft in bearing contact with the sidewalls of said apertures, a servomotor cylinder bore in contact with which said servo piston slides, an inlet connection formed in one end portion of the servo cylinder bore, a cutaway portion between the casing and the servo cylinder bore, and a lever extending from the swash plate through said cutaway portion to make connection with the servo piston, said cutaway portion also serving for the flow of liquid from said inlet connection into the casing and over said swashplate before entering the cylinders of the cylinder block.

2. A swashplate device comprising a rotary cylinder block having cylinders parallel to or inclined to the rotation axis, a tiltable swashplate, a one-piece transverse through shaft carrying the swash plate for tilting movement, a servo piston arranged to adjust the inclination of the swashplate about the axis of the transverse shaft, and a structural member formed in one piece and having a flat valve surface in contact with which the cylinder block rotates, a cylindrical bearing surface surrounding part of the cylinder block and in contact with which the cylinder block rotates, apertures which support said shaft in bearing contact with the sidewalls of said apertures, a servomotor cylinder bore in contact with which said servo piston slides, said servo piston defining a single working space within the servo cylinder, a pair of restrictors connected in series between a high-pressure port in the valve and a low-pressure zone, a connection between the junction of said pair of restrictors and the servo working space, an operative connection between the servo piston and the swashplate, and a rod extending through the servo cylinder for manual adjustment to adjust one of the pair of restrictors, the axis of the transverse one-piece through shaft being slightly offset from the cylinder block rotation axis in the sense that the torque generated by liquid at pressure within the cylinders on the swash plate is opposed by the pressure generated in the servo working space so that adjustment of said variable restrictor will cause adjustment of the angular setting of the swash plate. 

1. A swashplate device comprising a rotary cylinder block having cylinders parallel to or inclined to the rotation axis, a tiltable swashplate, a one-piece transverse through shaft carrying the swashplate for tilting movement, a servo piston arranged to adjust the inclination of the swashplate about the axis of the transverse shaft, and a structural member formed in one piece and having a flat valve surface in contact with which the cylinder block rotates, a cylindrical bearing surface surrounding part of the cylinder block and in contact with which the cylinder block rotates, apertures which support said shaft in bearing contact with the sidewalls of said apertures, a servomotor cylinder bore in contact with which said servo piston slides, an inlet connection formed in one end portion of the servo cylinder bore, a cutaway portion between the casing and the servo cylinder bore, and a lever extending from the swash plate through said cutaway portion to make connection with the servo piston, said cutaway portion also serving for the flow of liquid from said inlet connection into the casing and over said swashplate before entering the cylinders of the cylinder block.
 2. A swashplate device comprising a rotary cylinder block having cylinders parallel to or inclined to the rotation axis, a tiltable swashplate, a one-piece transverse through shaft carrying the swash plate for tilting movement, a servo piston arranged to adjust the inclination of the swashplate about the axis of the transverse shaft, and a structural member formed in one piece and having a flat valve surface in contact with which the cylinder block rotates, a cylindrical bearing surface surrounding part of the cylinder block and in contact with which the cylinder block rotates, apertures which support said shaft in bearing contact with the sidewalls of said apertures, a servomotor cylinder bore in contact with which said servo piston slides, said servo piston defining a single working space within the servo cylinder, a pair of restrictors connected in series between a high-pressure port in the valve and a low-pressure zone, a connection between the junction of said pair of restrictors and the servo working space, an operative connection between the servo piston and the swashplate, and a rod extending through the servo cylinder for manual adjustment to adjust one of the pair of restrictors, the axis of the transverse one-piece thRough shaft being slightly offset from the cylinder block rotation axis in the sense that the torque generated by liquid at pressure within the cylinders on the swash plate is opposed by the pressure generated in the servo working space so that adjustment of said variable restrictor will cause adjustment of the angular setting of the swash plate. 